Lincoln Cathedral - Wooden Trusses

Wooden Trusses

Wooden trusses offer a solid and reliable source of support for building because through their joints they are able to resist damage and remain strong. Triangles are the strongest shape because no matter where the force is being placed on them they are able to use their three joints to their fullest extent in order to withstand it. Making trusses with triangles inside larger triangles adds even more strength, as seen in Lincoln’s choir. The design of all wooden trusses is a tedious task as there are many different things that need to be considered while building these supports. There are many different ways that the trusses can fail if they are not designed or built properly; it is therefore crucial to design trusses that suit a specific building with specific needs in mind. The simplest form of a truss is an A frame; however, the great amount of outward thrust generated here often causes the truss to fail. The addition of a tie beam creates a triangular shape, although this beam can sometimes sag if the overall truss is too large. Neither one of these examples would have been suitable for Lincoln, owing to the sheer size of the roof. They would have failed to support the building, so collar beams and queen posts were added to the design in order to help prevent sagging. To protect against wind damage, braces were added. Secondary rafters were also added to the design to ensure that the weight was equally distributed. Saint Hugh’s Choir has a total of thirty six trusses keeping the roof in place, and it is held up entirely by means of its own weight and forces.